Magnetic resonance imaging apparatus and magnetic resonance imaging method

ABSTRACT

A magnetic resonance imaging apparatus according to an embodiment includes sequence controlling circuitry and processing circuitry. The sequence controlling circuitry is configured to execute (i) a first pulse sequence in which a spatially selective Inversion recovery (IR) pulse and a spatially non-selective IR pulse are applied, and subsequently an acquisition is performed and (ii) a second pulse sequence in which the spatially non-selective IR pulse is applied without applying the spatially selective IR pulse, and subsequently an acquisition is performed, while varying the first TI period, with respect to a plurality of first TI periods. The processing circuitry is configured to calculate a second TI period to be used in a third pulse sequence and a fourth pulse sequence, based on data obtained from the first pulse sequence and the second pulse sequence. The sequence controlling circuitry executes (iii) the third pulse sequence in which the spatially selective IR pulse and the spatially non-selective IR pulse are applied, and subsequently an acquisition is performed and (iv) the fourth pulse sequence in which the spatially non-selective IR pulse is applied without applying the spatially selective IR pulse, and subsequently an acquisition is performed. The processing circuitry generates a magnetic resonance image of an imaged region based on data obtained from the third pulse sequence and the fourth pulse sequence.

CROSS-REFERENCE TO RELATED APPLICATIONS Field

Embodiments described herein relate generally to a magnetic resonanceimaging apparatus and a magnetic resonance imaging method.

Background

Perfusion techniques are used for rendering hemodynamics of capillariesin a tissue by using an Arterial Spin Labeling (ASL) method by which aRadio Frequency (RF) pulse is radiated onto blood vessels so as toinvert blood spins and to use the inverted spins as an endogenoustracer. Known examples of the perfusion techniques include aFlow-sensitive Alternating Inversion Recovery (FAIR) method, aContinuous Arterial Spin Labeling (CASL) method, and a pulsed-ContinuousArterial Spin Labeling (pCASL) method.

The FAIR method is basically a two-dimensional imaging method by whichan imaging process is performed by applying a spatially selective pulseto a Region Of Interest (ROI) slice. Although the FAIR method has anadvantage of achieving a high Signal-to-Noise Ratio (SNR), a problemremains where, when a spatially selective IR pulse has repeatedly beenapplied, the perfusion curve fails to return to the original baselinethereof.

Further, by continuously applying a spatially selective pulse, the pCASLmethod is able to achieve a high SNR similarly to the FAIR method.However, the pCASL method has the problem where, when a spatiallyselective IR pulse has repeatedly been applied, the perfusion curvefails to return to the original baseline thereof. In addition, anotherproblem arises where it is necessary to suppress the MagnetizationTransfer (MT) effect, especially in brain.

For the reasons stated above, with the perfusion techniques using an ASLmethod, how to suppress the MT effect is important.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a magnetic resonance imaging apparatusaccording to an embodiment;

FIG. 2 is a flowchart illustrating a processing procedure performed bythe magnetic resonance imaging apparatus according to a firstembodiment;

FIGS. 3A and 3B are charts for explaining pulse sequences executed bythe magnetic resonance imaging apparatus according to the firstembodiment;

FIG. 3C is a drawing for explaining application regions of RadioFrequency (RF) pulses applied by the magnetic resonance imagingapparatus according to the first embodiment;

FIG. 3D is a drawing for explaining changes in longitudinalmagnetization caused by the RF pulses applied by the magnetic resonanceimaging apparatus according to the first embodiment;

FIG. 3E is a drawing for explaining k-space data acquisition performedby the magnetic resonance imaging apparatus according to the firstembodiment;

FIG. 4 is a drawing for explaining a Graphical User Interface (GUI)related to the magnetic resonance imaging apparatus according to thefirst embodiment;

FIG. 5 is a chart for explaining a process performed by the magneticresonance imaging apparatus according to the first embodiment;

FIGS. 6A, 6B, and 6C are charts for explaining pulse sequences executedby a magnetic resonance imaging apparatus according to a modificationexample of the first embodiment;

FIG. 7 is a flowchart illustrating a processing procedure performed by amagnetic resonance imaging apparatus according to a second embodiment;

FIG. 8 is a chart for explaining pulse sequences executed by themagnetic resonance imaging apparatus according to the second embodiment;and

FIGS. 9A and 9B are drawings for explaining a process performed by themagnetic resonance imaging apparatus according to another embodiment.

DETAILED DESCRIPTION

A magnetic resonance imaging apparatus according to an embodimentincludes sequence controlling circuitry and processing circuitry. Thesequence controlling circuitry is configured to execute (i) a firstpulse sequence in which a spatially selective inversion recovery (IR)pulse and a spatially non-selective IR pulse are applied, andsubsequently a Cartesian acquisition is performed when a first InversionTime (TI) period has elapsed, and a radial acquisition is performedafter the Cartesian acquisition and (ii) a second pulse sequence inwhich the spatially non-selective IR pulse is applied without applyingthe spatially selective IR pulse, and subsequently a Cartesianacquisition is performed when the first TI period has elapsed, and aradial acquisition is performed after the Cartesian acquisition, whilevarying the first TI period, with respect to a plurality of first TIperiods. The processing circuitry is configured to calculate a second TIperiod to be used in a third pulse sequence and a fourth pulse sequence,based on data obtained from the first pulse sequence and the secondpulse sequence executed by the sequence controlling circuitry. Thesequence controlling circuitry executes (iii) the third pulse sequencein which the spatially selective IR pulse and the spatiallynon-selective IR pulse are applied, and subsequently a Cartesianacquisition is performed when the second TI period has elapsed, and aradial acquisition is performed after the Cartesian acquisition and (iv)the fourth pulse sequence in which the spatially non-selective IR pulseis applied without applying the spatially selective IR pulse, andsubsequently a Cartesian acquisition is performed when the second TIperiod has elapsed, and a radial acquisition is performed after theCartesian acquisition. The processing circuitry generates a magneticresonance image of an imaged region based on data obtained from thethird pulse sequence and the fourth pulse sequence.

Exemplary embodiments of the present disclosure will be explained belowwith reference to the accompanying drawings. In the following sections,some of the constituent elements having mutually the same configurationswill be referred to by using the same reference characters, andduplicate explanations thereof will be omitted.

First Embodiment

FIG. 1 is a block diagram illustrating a magnetic resonance imagingapparatus 100 according to a first embodiment. As illustrated in FIG. 1, the magnetic resonance imaging apparatus 100 includes a staticmagnetic field magnet 101, a static magnetic field power supply (notillustrated), a gradient coil 103, a gradient power supply 104, a couch105, couch controlling circuitry 106, a transmission coil 107,transmitter circuitry 108, a reception coil 109, receiver circuitry 110,sequence controlling circuitry 120 (a sequence controlling unit), and animage processing device 130. The magnetic resonance imaging apparatus100 does not include an examined subject (hereinafter, “patient”) P(e.g., a human body). Further, the configuration illustrated in FIG. 1is merely an example. For instance, any of the functional units in thesequence controlling circuitry 120 and the image processing device 130may be integrated together or separated as appropriate.

The static magnetic field magnet 101 is a magnet formed to have a hollowand substantially circular cylindrical shape and is configured togenerate a static magnetic field in the space on the inside thereof. Forexample, the static magnetic field magnet 101 is a superconductivemagnet or the like and is magnetically excited by receiving a supply ofan electric current from the static magnetic field power supply. Thestatic magnetic field power supply is configured to supply the electriccurrent to the static magnetic field magnet 101. In another example, thestatic magnetic field magnet 101 may be a permanent magnet. In thatsituation, the magnetic resonance imaging apparatus 100 does not have toinclude a static magnetic field power supply. Further, the staticmagnetic field power supply may be provided separately from the magneticresonance imaging apparatus 100.

The gradient coil 103 is a coil formed to have a hollow andsubstantially cylindrical shape and is arranged on the inside of thestatic magnetic field magnet 101. The gradient coil 103 is formed bycombining together three coils corresponding to X-, Y-, and Z-axes thatare orthogonal to one another. By individually receiving a supply of anelectric current from the gradient power supply 104, each of the threecoils is configured to generate a gradient magnetic field of which themagnetic field intensity changes along the corresponding one of the X-,Y-, and Z-axes. The gradient magnetic fields generated by the gradientcoil 103 along the X-, Y-, and Z-axes are referred to as, for example, aslice gradient magnetic field Gs, a phase encode gradient magnetic fieldGe, and a readout gradient magnetic field Gr. The gradient power supply104 is configured to supply the electric current to the gradient coil103.

The couch 105 includes a couchtop 105 a on which the patient P isplaced. Under control of the couch controlling circuitry 106, thecouchtop 105 a is inserted into the hollow (an image taking opening) ofthe gradient coil 103, while the patient P is placed thereon. Normally,the couch 105 is installed so that the longitudinal direction thereofextends parallel to the central axis of the static magnetic field magnet101. Under control of the image processing device 130, the couchcontrolling circuitry 106 is configured to drive the couch 105 so as tomove the couchtop 105 a in longitudinal directions and up-and-downdirections.

The transmission coil 107 is arranged on the inside of the gradient coil103 and is configured to generate a radio frequency magnetic field byreceiving a supply of an RF pulse from the transmitter circuitry 108.The transmitter circuitry 108 is configured to supply the RF pulsecorresponding to a Larmor frequency determined by the type of targetedatoms and the magnetic field intensity, to the transmission coil 107.

The reception coil 109 is arranged on the inside of the gradient coil103 and is configured to receive magnetic resonance signals (whichhereinafter may be referred to as “MR signals” as necessary) emittedfrom the patient P due to influence of the radio frequency magneticfield. Upon receipt of the magnetic resonance signals, the receptioncoil 109 is configured to output the received magnetic resonance signalsto the receiver circuitry 110.

The transmission coil 107 and the reception coil 109 described above aremerely examples. The configuration may be realized by using one or acombination of two or more selected from among: a coil having onlytransmitting functions, a coil having only receiving functions, and acoil having transmitting and receiving functions.

The receiver circuitry 110 is configured to detect the magneticresonance signals output from the reception coil 109 and to generatemagnetic resonance data based on the detected magnetic resonancesignals. More specifically, the receiver circuitry 110 is configured togenerate the magnetic resonance data by performing a digital conversionon the magnetic resonance signals output from the reception coil 109.Further, the receiver circuitry 110 is configured to transmit thegenerated magnetic resonance data to the sequence controlling circuitry120. Alternatively, the receiver circuitry 110 may be provided so as tobelong to a gantry device including the static magnetic field magnet101, the gradient coil 103, and the like.

The sequence controlling circuitry 120 is configured to perform animaging process on the patient P, by driving the gradient power supply104, the transmitter circuitry 108, and the receiver circuitry 110,based on sequence information transmitted thereto from the imageprocessing device 130. In this situation, the sequence information isinformation defining a procedure for performing the imaging process. Thesequence information defines: the intensity of the electric current tobe supplied by the gradient power supply 104 to the gradient coil 103and the timing with which the electric current is to be supplied; theintensity of the RF pulse to be supplied by the transmitter circuitry108 to the transmission coil 107 and the timing with which the RF pulseis to be applied; the timing with which the magnetic resonance signal isdetected by the receiver circuitry 110; and the like. For example, thesequence controlling circuitry 120 may be an integrated circuit such asan Application Specific Integrated Circuit (ASIC) or a FieldProgrammable Gate Array (FPGA) or an electronic circuit such as aCentral Processing Unit (CPU) or a Micro Processing Unit (MPU). Detailsof pulse sequences executed by the sequence controlling circuitry 120will be explained later.

Further, upon receipt of the magnetic resonance data from the receivercircuitry 110 as a result of the imaging process performed on thepatient P by driving the gradient power supply 104, the transmittercircuitry 108, and the receiver circuitry 110, the sequence controllingcircuitry 120 is configured to transfer the received magnetic resonancedata to the image processing device 130.

The image processing device 130 is configured to control the entirety ofthe magnetic resonance imaging apparatus 100, to generate images, andthe like. The image processing device 130 includes a memory 132, aninput device 134, a display 135, and processing circuitry 150. Theprocessing circuitry 150 includes an interface function 131, acontrolling function 133, and a generating function 136.

In the first embodiment, the processing functions performed by theinterface function 131, the controlling function 133, and the generatingfunction 136 are stored in the memory 132 in the form ofcomputer-executable programs. The processing circuitry 150 is aprocessor configured to realize the functions corresponding to theprograms, by reading and executing the programs from the memory 132. Inother words, the processing circuitry 150 that has read the programs hasthe functions illustrated within the processing circuitry 150 in FIG. 1. Although the example is explained with reference to FIG. 1 in whichthe single processing circuit (i.e., the processing circuitry 150)realizes the processing functions performed by the interface function131, the controlling function 133, and the generating function 136, itis also acceptable to structure the processing circuitry 150 bycombining together a plurality of independent processors, so that thefunctions are realized as a result of the processors executing theprograms. In other words, each of the abovementioned functions may bestructured as a program, so that the single processing circuit (theprocessing circuitry 150) executes the programs. In another example, oneor more specific functions may each be installed in a dedicated andindependent program executing circuit. Further, in FIG. 1 , theinterface function 131, the controlling function 133, and the generatingfunction 136 are examples of a receiving unit, a controlling unit, and agenerating unit, respectively. Further, the sequence controllingcircuitry 120 is an example of a sequence controlling unit.

The term “processor” used in the above explanations denotes, forexample, a Central Processing Unit (CPU), a Graphical Processing Unit(GPU), or a circuit such as an Application Specific Integrated Circuit(ASIC) or a programmable logic device (e.g., a Simple Programmable LogicDevice [SPLD], a Complex Programmable Logic Device [CPLD], or a FieldProgrammable Gate Array [FPGA]). The one or more processors areconfigured to realize the functions by reading and executing theprograms saved in the memory 132.

Further, instead of saving the programs in the memory 132, it is alsoacceptable to directly incorporate the programs in the circuits of theone or more processors. In that situation, the one or more processorsrealize the functions by reading and executing the programs incorporatedin the circuits thereof. Similarly, the couch controlling circuitry 106,the transmitter circuitry 108, the receiver circuitry 110, and the likeare each also configured by using an electronic circuit like theabovementioned processor.

By employing the interface function 131, the processing circuitry 150 isconfigured to transmit the sequence information to the sequencecontrolling circuitry 120 and to receive the magnetic resonance datafrom the sequence controlling circuitry 120. Further, upon receipt ofthe magnetic resonance data, the processing circuitry 150 including theinterface function 131 is configured to store the received magneticresonance data into the memory 132.

The magnetic resonance data stored in the memory 132 is arranged in ak-space by the controlling function 133. As a result, the memory 132stores therein k-space data.

The memory 132 is configured to store therein the magnetic resonancedata received by the processing circuitry 150 including the interfacefunction 131, the k-space data arranged in the k-space by the processingcircuitry 150 including the controlling function 133, image datagenerated by the processing circuitry 150 including the generatingfunction 136, and the like. For example, the memory 132 may be asemiconductor memory element such as a Random Access Memory (RAM) or aflash memory, or a hard disk, an optical disk, or the like.

The input device 134 is configured to receive various types ofinstructions and inputs of information from an operator. For example,the input device 134 is a pointing device such as a mouse or atrackball, a selecting device such as a mode changing switch, and/or aninput device such as a keyboard. Under control of the processingcircuitry 150 including the controlling function 133, the display 135 isconfigured to display a Graphical User Interface (GUI) used forreceiving an input of an image taking condition, images generated by theprocessing circuitry 150 including the generating function 136, and thelike. For example, the display 135 is a display such as a liquid crystaldisplay monitor.

By employing the controlling function 133, the processing circuitry 150is configured to control the entirety of the magnetic resonance imagingapparatus 100 and to control image taking processes, image generatingprocesses, image displaying processes, and the like. For example, theprocessing circuitry 150 including the controlling function 133 isconfigured to receive the input of the image taking condition (e.g., animage taking parameter) through the GUI and to generate the sequenceinformation according to the received image taking condition. Further,the processing circuitry 150 including the controlling function 133 isconfigured to transmit the generated sequence information to thesequence controlling circuitry 120.

By employing the generating function 136, the processing circuitry 150is configured to generate an image by reading the k-space data from thememory 132 and performing a reconstructing process such as a Fouriertransform on the read k-space data.

Next, a background of an embodiment will briefly be explained.

Perfusion techniques are used for rendering hemodynamics of capillariesin a tissue by using an Arterial Spin Labeling (ASL) method by which anRF pulse is radiated onto blood vessels so as to invert blood spins andto use the inverted spins as an endogenous tracer. Known examples of theperfusion techniques include a Flow-sensitive Alternating InversionRecovery (FAIR) method, a Continuous Arterial Spin Labeling (CASL)method, and a pulsed-Continuous Arterial Spin Labeling (pCASL) method.

The FAIR method is basically a two-dimensional imaging method by whichan imaging process is performed by applying a spatially selective pulseto a ROI slice. Although the FAIR method has an advantage of achieving ahigh SNR, a problem remains where, when a spatially selective IR pulsehas repeatedly been applied, the perfusion curve fails to return to theoriginal baseline thereof.

Further, by continuously applying a spatially selective pulse, the pCASLmethod is able to achieve a high SNR similarly to the FAIR method.However, the pCASL method has the problem where, when a spatiallyselective IR pulse has repeatedly been applied, the perfusion curvefails to return to the original baseline thereof. In addition, anotherproblem arises where it is necessary to suppress the MagnetizationTransfer (MT) effect.

For the reasons stated above, with the perfusion techniques using an ASLmethod, how to suppress the MT effect is important.

In relation to the above, among ASL methods, configurations to apply aspatially non-selective IR pulse have not been mainstream methods,because spatially non-selective IR pulses can easily lower the SN ratiosof images. However, we have discovered that applying a spatiallynon-selective IR pulse significantly suppresses the MT effect. One ofthe reasons is that, although a larger MT effect is exerted onmagnetization while spins are aligned along the direction of a magneticfield (+Mz), a smaller MT effect is exerted on longitudinalmagnetization of longitudinal magnetization in the opposite direction(−Mz).

Accordingly, the magnetic resonance imaging apparatus 100 according toan embodiment is configured to execute two pulse sequences, namely, apulse sequence in which a spatially non-selective pulse is applied, andsubsequently an acquisition sequence is executed and another pulsesequence in which a spatially non-selective pulse and a spatiallyselective pulse are applied and subsequently an acquisition sequence isexecuted and is configured to generate a magnetic resonance image bycalculating a difference between pieces of data acquired from the twopulse sequences. In this situation, as the acquisition sequence, thesequence controlling circuitry 120 performs a Cartesian acquisition andsubsequently performs a radial acquisition, in an example.

As a result, it is possible to suppress the MT effect and to apply ASLto a site other than the heart, which has hitherto been considereddifficult. It is therefore possible to perform four-dimensional (4D)non-contrast-enhanced ASL imaging on, for example, a region in thebrain, a muscle, or a kidney, a region including a region havingmicrovascularization, or a region including a region havingmicrocirculation.

In addition, it is possible to perform a preliminary imaging processwith respect to a plurality of TI values and to determine an optimal TIvalue based on the results thereof. It is therefore possible to improvethroughput of medical examinations.

Further, by combining the 4D non-contrast-enhanced ASL imaging withMagnetic Resonance Angiography (MRA), it is expected possible to predictof a stenosis or an occlusion of a blood vessel with a high level ofprecision.

A configuration to realize this example will be explained with referenceto FIGS. 2 to 5 .

FIG. 2 is a flowchart for explaining a flow in a process performed bythe magnetic resonance imaging apparatus according to the firstembodiment.

To begin with, at step S100, the sequence controlling circuitry 120executes: a first pulse sequence in which a spatially selective IR pulseand a spatially non-selective IR pulse are applied and subsequently aradial acquisition is performed; and a second pulse sequence in which aspatially non-selective IR pulse is applied without applying a spatiallyselective IR pulse, and subsequently a radial acquisition is performed.

This procedure will be explained with reference to FIGS. 3A to 3E.

FIG. 3A illustrates the first pulse sequence in which the spatiallyselective IR pulse and the spatially non-selective IR pulse are applied,and subsequently the radial acquisition is performed. FIG. 3Billustrates the second pulse sequence in which, without applying aspatially selective IR pulse, the radial acquisition is performed. Thefirst pulse sequence in which the spatially selective IR pulse and thespatially non-selective IR pulse are applied, and subsequently theradial acquisition is performed may be referred to as a Tag-ON sequence.In contrast, the second pulse sequence in which, without applying aspatially selective IR pulse, the radial acquisition is performed may bereferred to as a Tag-OFF sequence.

In the following sections, an example will be explained with referenceto FIGS. 3A and 3B in which the acquisition sequences executed by thesequence controlling circuitry 120 at step S100 are for minimizingacoustic noise utilizing Ultrashort Echo Time (mUTE). Usually, thesequence controlling circuitry 120 is configured to link together theTag-ON sequence in FIG. 3A and the Tag-OFF sequence in FIG. 3B, so as toexecute the linked sequences as a set of acquisitions.

As illustrated in FIG. 3A, the sequence controlling circuitry 120performs a magnetic resonance imaging process on an imaged region, byexecuting the first pulse sequence in which a spatially non-selective IRpulse 4, which is an RF pulse to invert nuclear spins in a wider region,is applied to a wider region including the imaged region, andsubsequently, a spatially selective IR pulse 5, which is an RF pulse toinvert nuclear spins in a specific region, is applied to a smallerregion than the application region of the spatially non-selective IRpulse 4, and when a prescribed time period has elapsed, the acquisitionsequence to acquire data is executed.

At first, the application regions of the spatially non-selective IRpulse 4 and the spatially selective IR pulse 5 will be explained, withreference to FIG. 3C. In this situation, a region 8 denotes the imagedregion, which is the region subject to the imaging process and theregion from which the data is to be acquired with the acquisitionsequence executed by the sequence controlling circuitry 120 after thespatially non-selective IR pulse 4 and the spatially selective IR pulse5 are applied. Further, a region 6 denotes the region to which thespatially non-selective IR pulse is applied by the sequence controllingcircuitry 120. The sequence controlling circuitry 120 is configured toapply the spatially non-selective IR pulse 4 to the wider region 6including the region 8 serving as the imaged region. Further, a region 7denotes the region to which the spatially selective IR pulse 5 isapplied by the sequence controlling circuitry 120. The sequencecontrolling circuitry 120 is configured to apply the spatially selectiveIR pulse 5 to the region 7, which is a relatively smaller region. Theregion 7 to which the spatially selective IR pulse 5 is applied by thesequence controlling circuitry 120 is, for example, selected on theupstream side of the region 8 serving as the imaged region. In otherwords, blood that is present in the region 7 at the time of applying thespatially selective IR pulse 5 and is present in the region 8 at thetime of executing the acquisition sequence is labeled.

Next, changes in longitudinal magnetization of spins caused by theapplications of the spatially non-selective IR pulse 4 and the spatiallyselective IR pulse 5 will be explained, with reference to FIG. 3D. FIG.3D is a drawing for explaining temporal changes in the longitudinalmagnetization of the spins.

The plotline 14 indicates temporal changes in the longitudinalmagnetization of the spins in a location to which both the spatiallynon-selective IR pulse 4 and the spatially selective IR pulse 5 areapplied. The plotline 13 indicates temporal changes in the longitudinalmagnetization of the spins in a location to which only the spatiallynon-selective IR pulse 4 is applied, while the spatially selective IRpulse 5 is not applied.

Both the spatially non-selective IR pulse 4 and the spatially selectiveIR pulse 5 invert the longitudinal magnetization of the location towhich the RF pulse is applied. Accordingly, in the location to whichboth the spatially non-selective IR pulse 4 and the spatially selectiveIR pulse 5 are applied, i.e., the labeled location, the longitudinalmagnetization is inverted twice so that the longitudinal magnetizationreturns to the original value and exhibits a high signal, as indicatedby the plotline 14.

In contrast, in the location to which only the spatially non-selectiveIR pulse 4 is applied, while the spatially selective IR pulse 5 is notapplied, i.e., the location such as a background part, the signal of thelongitudinal magnetization is inverted by the RF pulse only once, andthe signal gradually relaxes, as indicated by the plotline 13. In thissituation, the longitudinal magnetization value is equal to zero at anull point 15. Accordingly, when the sequence controlling circuitry 120executes the acquisition sequence in the vicinity of the null point 15,because the blood labeled by the spatially selective IR pulse 5 exhibitsa high signal, it is possible to perform the imaging process whilesuppressing background signals. A purpose of the spatially non-selectiveIR pulse 4 and the spatially selective pulse 5 applied by the sequencecontrolling circuitry 120 has thus been explained.

Next, with reference back to FIG. 3A, the acquisition sequence executedby the sequence controlling circuitry 120 will be explained. In thefirst embodiment, the sequence controlling circuitry 120 performs a 4Dacquisition. In this situation, the 4D acquisition denotes performing athree-dimensional (3D) acquisition on the k-space while varying the TIperiods, so as to perform acquisition four-dimensionally in total. Inother words, by varying the TI period to be different values, thesequence controlling circuitry 120 is configured to acquire data withrespect to a plurality of TI periods each of which denotes the timesince the spatially non-selective pulse 4 or the spatially selectivepulse 5 is applied. In this situation, for example, the sequencecontrolling circuitry 120 acquires the data by using a mUTE sequence asthe acquisition sequence. In other words, in the first embodiment, theacquisition sequence executed by the sequence controlling circuitry 120includes: acquisitions in a plurality of Cartesian segments such asCartesian acquisitions 15 a, 15 b, 15 c, 15 d, 15 e, and 15 f performedon a central part of the space; and a radial acquisition 16 performed onan outside part of the k-space. In other words, after applying thespatially non-selective IR pulse 4 and the spatially selective IR pulse5, the sequence controlling circuitry 120 performs the Cartesianacquisition 15 a when time 16 a has elapsed, performs the Cartesianacquisition 15 b when time 16 b has elapsed, performs the Cartesianacquisition 15 c when time 16 c has elapsed, performs the Cartesianacquisition 15 d when time 16 d has elapsed, similarly performs theCartesian acquisitions 15 e and 15 f, and subsequently performs theradial acquisition 16.

FIG. 3E illustrates a relationship between the Cartesian acquisitionsand the radial acquisition performed by the sequence controllingcircuitry 120. FIG. 3E three-dimensionally illustrates the region of thek-space where the data acquisition is performed. A region 60 representsthe central part of the k-space where the Cartesian acquisitions areperformed. Each of the line segments such as a line segment 61 indicatesthe radial acquisition performed by the sequence controlling circuitry120. In other words, in the executed acquisition sequence, the sequencecontrolling circuitry 120 at first performs the Cartesian acquisitions15 a, 15 b, 15 c, 15 d, 15 e, and 15 f, on the region 60 in the centralpart of the k-space while varying the TI value, and subsequentlyperforms the radial acquisition 16 on the region outside the region 60positioned in the central part of the k-space, toward the outside fromthe center of the k-space, for example. In this manner, the sequencecontrolling circuitry 120 has executed the first pulse sequence.

At step S110 explained later, by employing the generating function 136,the processing circuitry 150, for example, generates data related toTI=TI1 being the TI corresponding to the time 16 a by using theacquisition from the cartesian acquisition 15 a and the radialacquisition 16, further generates data related to TI=TI2 being the TIcorresponding to the time 16 b by using the acquisition from thecartesian acquisition 15 b and the radial acquisition 16, and generatesdata related to TI=TI3 being the TI corresponding to the time 16 c byusing the acquisition from the cartesian acquisition 15 c and the radialacquisition 16.

Similarly as illustrated in FIG. 3B, in the second pulse sequence, afterapplying only the spatially non-selective IR pulse 4 without applyingthe spatially selective IR pulse 5, the sequence controlling circuitry120 performs a cartesian acquisition 15 a when the time 16 a haselapsed, performs a cartesian acquisition 15 b when the time 16 b haselapsed, performs a Cartesian acquisition 15 c when the time 16 c haselapsed, performs a Cartesian acquisition 15 d when the time 16 d haselapsed, similarly performs Cartesian acquisitions 15 e and 15 f, andsubsequently performs a radial acquisition 16. The only differencebetween the first pulse sequence and the second pulse sequence is thepresence/absence of the application of the spatially selective pulse 5,and the other processes are the same.

In FIGS. 3A and 3B, the time TI1, TI2, TI3, TI4 and so on, which denotethe time from the application of the spatially non-selective pulse 4 orthe spatially selective pulse 5 to the execution of the Cartesianacquisitions 15 a, 15 b, 15 c, 15 d, 15 e, and 15 f, are variable andmay arbitrarily be set in accordance with instructions from the user.FIG. 4 illustrates an example of a GUI for this purpose.

By employing the controlling function 133, the processing circuitry 150receives a change made to TI1, i.e., an input of the time 16 a in FIGS.3A and 3B, via the input device 134 and buttons 21 and 22 on an inputpanel 20 of the display 135. Further, by employing the controllingfunction 133, the processing circuitry 150 receives a change made to anincrement of the TI, e.g., an input of the increment from TI1 to TI2illustrated in FIGS. 3A and 3B, via the input device 134 and buttons 23and 24 on the input panel 20 of the display 135. Further, by employingthe controlling function 133, the processing circuitry 150 receives achange made to the number of cartesian acquisition segments, via theinput device 134 and buttons 25 and 26 on the input panel 20 of thedisplay 135. In this situation, the number of Cartesian acquisitionsegments denotes the number of Cartesian acquisition segmentscorresponding to mutually-different TI values. In the exampleillustrated in FIGS. 3A and 3B, the number of Cartesian acquisitionsegments is six. Further, by employing the controlling function 133, theprocessing circuitry 150 receives a change made to a Cartesianacquisition interval via the input device 134 and buttons 27 and 28 onthe input panel 20 of the display 135. In this situation, the Cartesianacquisition interval denotes the interval between the Cartesianacquisitions performed by the sequence controlling circuitry 120. Aninterval 17 illustrated in FIG. 3B is the Cartesian acquisitioninterval.

Subsequently, at step S120, by employing the generating function 136,the processing circuitry 150 generates a magnetic resonance image inwhich the MT effect is suppressed, based on the data obtained from thefirst pulse sequence and the second pulse sequence executed by thesequence controlling circuitry 120 at step S100. More specifically, byemploying the generating function 136, the processing circuitry 150generates a first image (a Tag-ON image) by performing a Fouriertransform on first k-space data obtained by executing the first pulsesequence being a Tag-ON sequence.

For example, by employing the generating function 136, the processingcircuitry 150 generates data related to TI=TI1, based on the dataobtained from the Cartesian acquisition 15 a and the data obtained fromthe radial acquisition 16 in FIG. 3A. Similarly, by employing thegenerating function 136, the processing circuitry 150 generates datarelated to TI=TI2, based on the data obtained from the Cartesianacquisition 15 b and the data obtained from the radial acquisition 16 inFIG. 3A. Further, by employing the generating function 136, theprocessing circuitry 150 generates data related to TI=TI3, based on thedata obtained from the Cartesian acquisition 15 c and the data obtainedfrom the radial acquisition 16 in FIG. 3A. In this manner, theprocessing circuitry 150 generates the pieces of data related to theplurality of TI values, based on the pieces of data obtained byexecuting the first pulse sequence.

Further, by employing the generating function 136, the processingcircuitry 150 generates a second image (a Tag-OFF image) by performing aFourier transform on second k-space data obtained by executing thesecond pulse sequence being a Tag-OFF sequence. Subsequently, theprocessing circuitry 150 generates a magnetic resonance image in whichthe background signal and the MT effect are suppressed by performing adifference calculating process between the first image (the Tag-ONimage) and the second image (the Tag-OFF image).

For example, by employing the generating function 136, the processingcircuitry 150 generates data related to TI being equal to TI1, based onthe data obtained from the Cartesian acquisition 15 a and the dataobtained from the radial acquisition 16 in FIG. 3B. Similarly, byemploying the generating function 136, the processing circuitry 150generates data related to TI being equal to TI2, based on the dataobtained from the Cartesian acquisition 15 b and the data obtained fromthe radial acquisition 16 in FIG. 3B. Further, by employing thegenerating function 136, the processing circuitry 150 generates datarelated to TI being equal to TI3, based on the data obtained from theCartesian acquisition 15 c and the data obtained from the radialacquisition 16 in FIG. 3B. In this manner, the processing circuitry 150has generated the pieces of data related to the plurality of TI values,based on the pieces of data obtained by executing the first pulsesequence.

As explained above, in the magnetic resonance imaging apparatus 100according to the first embodiment, the 4D ASL sequence is executed byapplying the spatially non-selective IR pulse. As a result, it ispossible to suppress the MT effect and is therefore possible to applyASL to a site other than the heart, which has hitherto been considereddifficult. For example, it is possible to perform the imaging process onan imaged region such as a region in the brain, a muscle, or a kidney, aregion including a region having microvascularization, or a regionincluding a region having microcirculation.

The example was explained with reference to FIGS. 3A and 3B in which theradial acquisition 16 is performed after the Cartesian acquisitions 15 ato 15 f; however, possible embodiments are not limited to this example.The radial acquisition 16 may be performed before the Cartesianacquisitions 15 a to 15 f. In other words, the radial acquisition 16 maybe performed before the application of the ASL pulse.

In addition, by further analyzing the magnetic resonance image generatedat step S110, the processing circuitry 150 is capable of distinguishinga normal blood flow from a blood vessel having a stenosis, beingischemic, having an occlusion, having an infarct, or having beenrevascularized/treated.

In an example, by employing the generating function 136, the processingcircuitry 150 is configured to calculate, with respect to the imagedregion, at least one of a peak signal value, a peak flow time, arterialtransit time, and a blood flow volume, as an index, based on the dataobtained from the first pulse sequence and the second pulse sequenceexecuted by the sequence controlling circuitry 120 at step S100 and isconfigured to further perform the analysis based on the calculatedindex.

FIG. 5 illustrates an example of the analysis. FIG. 5 illustratestemporal changes in signal values observed after the differencecalculating process performed between the first image and the secondimage, in various status of blood vessels, with respect to a givenimaged region. More specifically, the curve 50 indicates temporalchanges in the signal value of a normal blood flow. The curve 51indicates temporal changes in the signal value of a blood flow in ablood vessel in a stenosed/ischemic state. The curve 52 indicatestemporal changes in the signal value of a blood flow in a blood vesselhaving a tighter stenosis. The curve 53 indicates temporal changes inthe signal value of a blood flow in a blood vessel in anoccluded/infarct state. The curve 54 indicates temporal changes in thesignal value of a blood flow in a blood vessel that has beenrevascularized/treated.

In this situation, as for the peak flow time at which the signal valueof a blood flow exhibits a maximum value, it is observed in comparisonwith a peak flow time 55 of the signal value of the blood flow in thenormal blood vessel, the peak flow time of the curve 51 indicating thesignal value of the blood flow in the blood vessel in thestenosis/ischemic state has the TI shifted to later and thus has aslower blood flow. Further, the peak flow time of the curve 52indicating the signal value of the blood flow in the blood flow having atighter stenosis is further later than the peak flow time of the curve51. Conversely, the peak flow time of the curve 54 indicating the signalvalue of the blood flow in the blood vessel that has beenrevascularized/treated is shifted in the direction of smaller TI values,compared to the peak flow time 55 of the signal value of the blood flowin the normal blood vessel. As explained herein, the processingcircuitry 150 is able to predict the degree of a stenosis or anocclusion of the blood vessel while employing the generating function136, by utilizing the notion that the peak flow time of the signal valuevaries depending on the degree of a stenosis or an occlusion in theblood vessel. In other words, by employing the generating function 136,the processing circuitry 150 is able to predict the degree of thestenosis or the occlusion in the blood vessel, based on the indexacquired based on the data obtained from the first pulse sequence andthe second pulse sequence executed by the sequence controlling circuitry120 at step S100.

The example was explained above in which, by employing the generatingfunction 136, the processing circuitry 150 is configured to predict thedegree of the stenosis or the occlusion of the blood vessel by using thepeak flow time as an index; however, possible embodiments are notlimited to this example. In other examples, by employing the generatingfunction 136, the processing circuitry 150 may predict the degree of astenosis or an occlusion of the blood vessel by using, as an index, apeak signal value, arterial transit time (ATT) 56, or a blood flowvolume obtained by calculating the area of the part defined by the curveand the horizontal axis (the time axis). For example, a tighter stenosisexhibits a delayed peak flow time, a smaller peak signal value, andlonger ATT, the sequence controlling circuitry 120 is able to predictthe degree of a stenosis or an occlusion of the blood vessel based onthese characteristics. In particular, the magnetic resonance imagingapparatus 100 according to the embodiment is capable of efficientlyeliminating the background signal and the MT signal by performing thedifference calculating process on the images obtained from the two pulsesequences executed with the application of the spatially non-selectiveIR pulse. Consequently, by employing the generating function 136, thesequence controlling circuitry 120 is able to detect even a tightstenosis equal to or smaller than 50% of the diameter of the bloodvessel, based on the index.

As explained above, the magnetic resonance imaging apparatus accordingto the first embodiment is able to obtain a perfusion signal in whichthe MT effect is suppressed.

Modification Examples of First Embodiment

In the first embodiment, the example was explained in which the sequencecontrolling circuitry 120 implements the process of minimizing acousticnoise utilizing Ultrashort Echo Time (mUTE); however, possibleembodiments are not limited to this example. The sequence controllingcircuitry 120 may execute any of various types of 2D and 3D acquisitionsequences, such as a Fast Spin Echo (FSE) method, a Fast Asymmetric SpinEcho (FASE) method, balanced Steady State Free Precession (bSSFP), anUltrashort Echo Time (UTE) method, an Echo Planar Imaging (EPI) method,or the like.

Further, for the imaging process, the sequence controlling circuitry 120may implement electrocardiographic synchronization.

FIGS. 6A, 6B, and 6C illustrate examples thereof.

As schematically illustrated in FIG. 6A, when the sequence controllingcircuitry 120 is configured to implement the electrocardiographicsynchronization, the sequence controlling circuitry 120 alternatelyexecutes a Tag-ON sequence 1 and a Tag-OFF sequence 2 in synchronizationwith an electrocardiogram 10. In this situation, FIG. 6B illustrates anexample of the Tag-ON sequence 1, whereas FIG. 6C illustrates an exampleof the Tag-OFF sequence 2. In this situation, as for the processes otherthan the electrocardiographic synchronization, the sequence controllingcircuitry 120 and the processing circuitry 150 perform the sameprocesses as those in the first embodiment.

In other words, as illustrated in FIG. 6B, the sequence controllingcircuitry 120 applies the spatially non-selective pulse 4 when aprescribed time period 11 has elapsed since an R-wave 3 and executes anacquisition sequence 16 when a prescribed time period 12 has elapsedsince the application of the spatially non-selective pulse 4.

Further, as illustrated in FIG. 6C, the sequence controlling circuitry120 applies the spatially non-selective pulse 4 and the spatiallyselective pulse 5 when the prescribed time period 11 has elapsed sincean R-wave 3 and executes an acquisition sequence 16 when the prescribedtime period 12 has elapsed since the application of the spatiallynon-selective pulse 4 and the spatially selective pulse 5.

Second Embodiment

In a second embodiment, an example will be explained in which, similarlyto the first embodiment, the sequence controlling circuitry 120 performsan imaging process while applying the spatially non-selective pulse inboth a Tag-ON sequence and a Tag-OFF sequence, but performs prior to amain imaging process, a preliminary scan multiple times forunderstanding an optimal TI period while varying the TI period. As aresult, it is possible to perform the main imaging process by using theTI period that is most appropriate for the purpose of the imagingprocess.

Next, this process will be explained with reference to FIG. 7 . FIG. 7is a flowchart illustrating a processing procedure performed by amagnetic resonance imaging apparatus according to the second embodiment.In FIG. 7 , duplicate explanations of the parts having the sameprocesses as those in the first embodiment will be omitted.

To begin with, at step S200, the sequence controlling circuitry 120executes the first pulse sequence being a Tag-ON pulse sequence and thesecond pulse sequence being a Tag-OFF pulse sequence, while applying thespatially non-selective IR pulse and varying the TI period, with respectto a plurality of TI periods.

FIG. 8 illustrates an example of this process.

As illustrated in FIG. 8 , the sequence controlling circuitry 120executes: the Tag-ON sequence 1 being the first pulse sequence in whichthe spatially selective IR pulse 5 and the spatially non-selective IRpulse 4 are applied, and subsequently, a data acquisition 16 isperformed when the first TI period has elapsed; and the Tag-OFF sequence2 being the second pulse sequence in which the spatially non-selectiveIR pulse 4 is applied without applying the spatially selective IR pulse5, and subsequently, a data acquisition 16 is performed when the TIperiod has elapsed, while varying the TI period, with respect to aplurality of TI periods e.g., TI periods 16 a, 16 b, and so on. In thissituation, for example, the sequence controlling circuitry 120 executes:the Tag-ON sequence 1 being the first pulse sequence in which thespatially selective IR pulse 5 and the spatially non-selective IR pulse4 are applied, and subsequently, a Cartesian acquisition is performedwhen the TI period has elapsed, and a radial acquisition is performedafter the Cartesian acquisition; and the Tag-OFF sequence 2 being thesecond pulse sequence in which the spatially non-selective IR pulse isapplied without applying the spatially selective IR pulse, andsubsequently, a Cartesian acquisition is performed when the TI periodhas elapsed, and a radial acquisition is performed after the Cartesianacquisition, while varying the TI period, with respect to the pluralityof TI periods e.g., the TI periods 16 a, 16 b, and so on.

After that, at step S210, by employing the generating function 136, theprocessing circuitry 150 calculates, based on data obtained from thefirst pulse sequence and the second pulse sequence, a TI period or a setof TI periods to be used in a third pulse sequence being a Tag-ONsequence and a fourth pulse sequence being a Tag-OFF sequence that willbe executed by the sequence controlling circuitry 120 at step S220. Inthis situation, an example of the pulse sequence executed as the thirdpulse sequence being the Tag-ON sequence to be executed by the sequencecontrolling circuitry 120 at step S220 is the pulse sequence in FIG. 3Aexplained in the first embodiment. Further, an example of the pulsesequence executed as the fourth pulse sequence being the Tag-OFFsequence to be executed by the sequence controlling circuitry 120 atstep S230 is the pulse sequence in FIG. 3B explained in the firstembodiment.

As a method for calculating the TI period or the set of TI periods to beused in the third pulse sequence and the fourth pulse sequence, forexample, the processing circuitry 150 may receive an input from the uservia the input device 134 by employing the controlling function 133. Asanother method, by employing the controlling function 133, theprocessing circuitry 150 may calculate an index such as a peak signalvalue, a peak flow time, arterial transit time, a blood flow volume, orthe like of the imaged region based on the first pulse sequence and thesecond pulse sequence, as explained in the first embodiment, so as tofurther calculate the TI period or the set of TI periods to be used inthe third pulse sequence and the fourth pulse sequence based on thecalculated index.

Subsequently, at step S220, the sequence controlling circuitry 120executes the third pulse sequence being a Tag-ON sequence and the fourthpulse sequence being a Tag-OFF sequence, while applying the spatiallynon-selective IR pulse, with respect to the TI period or the set of TIperiods calculated at step S210. In an example, the sequence controllingcircuitry 120 executes: the third pulse sequence in which the spatiallyselective IR pulse and the spatially non-selective pulse are applied,and subsequently, a Cartesian acquisition is performed when the TIperiod (or the set of TI periods) calculated at step S210 has elapsed,and a radial acquisition is performed after the Cartesian acquisition;and the fourth pulse sequence in which the spatially non-selective IRpulse is applied without applying the spatially selective IR pulse, andsubsequently, a Cartesian acquisition is performed when the TI period(or the set of TI periods) has elapsed, and a radial acquisition isperformed after the Cartesian acquisition.

After that, at step S230, by employing the generating function 136, theprocessing circuitry 150 generates a magnetic resonance imaging image ofthe imaged region based on data obtained from the third pulse sequenceand the fourth pulse sequence.

The process at step S220 and the process at step S230 are the same asthe processes in the first embodiment. Accordingly, duplicateexplanations thereof will be omitted.

Similarly to the first embodiment, by applying the spatiallynon-selective pulse at step S220, the magnetic resonance imagingapparatus 100 according to the embodiment is able to suppress the MTeffect. It is therefore possible to use, as the imaged region, a regionother than the heart such as a region in the brain, a muscle, or akidney, a region including microvascularization, a region includingmicrocirculation, or the like. Further, similarly to the firstembodiment, by employing the generating function 136, the processingcircuitry 150 is able to calculate the peak signal value, the peak flowtime, the arterial transit time, the blood flow volume, or the like ofthe imaged region as the index, based on the data obtained from thethird pulse sequence and the fourth pulse sequence. It is thereforepossible to predict the degree of a stenosis or an occlusion of theblood vessel, an abnormality in a perforator branch, or the like basedon the calculated index.

Other Embodiments

Possible embodiments are not limited to the above examples.

The magnetic resonance imaging apparatus 100 according to an embodimentmay, for example, predict the degree of a stenosis or an occlusion of ablood vessel or an abnormality in a perforator branch, based on an imageof the blood vessel obtained by Magnetic Resonance Angiography (MRA)implemented with a Time of Flight (TOF) method, together with the indexof the imaged region explained in the first embodiment such as a peaksignal value, a peak flow time, arterial transit time, a blood flowvolume, or the like.

This example will be explained, with reference to FIGS. 9A and 9B. FIGS.9A and 9B illustrate images of Magnetic Resonance Angiography (MRA)using a 3D TOF method. FIG. 9A illustrates a coronal image of the brain,whereas 9B illustrates an axial image of the brain. In FIG. 9A, althougha low-signal region 40 of an MRA signal is observed, it may be difficultin some situations, for example, to judge an abnormality in a perforatorbranch or the like from the MRA data alone, because microvascularizationnaturally has a low signal. To cope with this situation, for example, itis possible to predict an abnormality in a perforator branch, when ahypoperfusion signal is obtained as the magnetic resonance signalobtained by executing the pulse sequences in the first or the secondembodiment on the thalamus 41, which is a region related to the bloodvessels in the low-signal region 40 of the MRA signal. In other words,the magnetic resonance imaging apparatus 100 according to the embodimentis able to predict the degree of a stenosis or an occlusion of the bloodvessel or an abnormality in a perforator branch, by performing acomprehensive evaluation using the index calculated by the processingcircuitry 150 while employing the generating function 136, together withthe MRA image. In other words, based on a relationship between theposition of the parenchyma of the brain and blood vessel informationobtained from the MRA image or the like, for example, the magneticresonance imaging apparatus 100 according to the embodiment is able toidentify the position of a blood vessel that affects the normal/abnormalstate of the parenchyma of the brain and is thus able to predict thestatus of progress of a disease or the like, for example.

Further, in the first embodiment, the 4D imaging method is not limitedto performing a 3D acquisition while varying the TI value and may be a3D Cine acquisition, for example.

Computer Programs

The instructions in the processing procedure described in the aboveembodiments may be executed based on a computer program (hereinafter“program”) realized with software. As a result of a general-use computerstoring therein the program in advance and reading the program, it ispossible to achieve the same advantageous effects as those achieved bythe magnetic resonance imaging apparatus 100 according to any of theabove embodiments. The instructions described in the above embodimentsmay be recorded as a computer-executable program on a magnetic disk(e.g., a flexible disk or a hard disk), an optical disk (e.g., a CompactDisk Read-Only Memory [CD-ROM], a CD Recordable [CD-R], a CD ReWritable[CD-RW], a Digital Versatile Disk Read-Only Memory [DVD-ROM], a DVDRecordable [DVD±R], DVD ReWritable [DVD±RW]), a semiconductor memory, ora similar recording medium. Any storage format may be used as long asthe storage medium is readable by a computer or an embedded system. Byreading the program from the recording medium and causing a CPU toexecute the instructions written in the program based on the readprogram, the computer is able to realize the same operations as thoseperformed by the magnetic resonance imaging apparatus 100 according toany of the above embodiments. Further, when the computer obtains orreads the programs, the program may be obtained or read via a network.

Further, based on the instructions in the program installed in thecomputer or the embedded system from the storage medium, an OperatingSystem (OS) working in the computer or Middleware such as databasemanagement software or a network may execute a part of the processes forrealizing any of the above embodiments. Further, the storage medium doesnot necessarily have to be independent of the computer or the embeddedsystem and may be a storage medium storing therein or temporarilystoring therein the program transmitted via a Local Area Network (LAN),the Internet, or the like and downloaded. Further, the storage mediumdoes not necessarily have to be singular. Possible embodiments of thestorage medium include the situation where the processes of the aboveembodiments are executed from two or more media. It is possible to useany configuration for the one or more media.

The computer or the embedded system according to the above embodimentsis configured to execute the processes in the above embodiments based onthe program stored in the one or more storage media and may beconfigured as a single apparatus such as a personal computer or amicrocomputer or as a system in which a plurality of apparatuses isconnected together via a network. Further, the “computer” according tothe embodiments does not necessarily have to be a personal computer andmay be an arithmetic processing device included in an informationprocessing device or a microcomputer. The term “computer” is a genericname for any device or apparatus capable of realizing the functions ofthe embodiments by using the program.

According to at least one aspect of the embodiments described above, itis possible to suppress the MT effect.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A magnetic resonance imaging apparatus, comprising: sequence controlling circuitry configured to execute (i) a first pulse sequence in which a spatially selective inversion recovery (IR) pulse and a spatially non-selective IR pulse are applied, and subsequently a Cartesian acquisition is performed when a first Inversion Time (TI) period has elapsed, and a radial acquisition is performed after the Cartesian acquisition, and (ii) a second pulse sequence in which the spatially non-selective IR pulse is applied without applying the spatially selective IR pulse, and subsequently a Cartesian acquisition is performed when the first TI period has elapsed, and a radial acquisition is performed after the Cartesian acquisition, while varying the first TI period, with respect to a plurality of first TI periods; and processing circuitry configured to calculate a second TI period to be used in a third pulse sequence and a fourth pulse sequence, based on data obtained from the first pulse sequence and the second pulse sequence executed by the sequence controlling circuitry, wherein the sequence controlling circuitry is further configured to execute (iii) the third pulse sequence in which the spatially selective IR pulse and the spatially non-selective IR pulse are applied, and subsequently a Cartesian acquisition is performed when the second TI period has elapsed, and a radial acquisition is performed after the Cartesian acquisition, and (iv) the fourth pulse sequence in which the spatially non-selective IR pulse is applied without applying the spatially selective IR pulse, and subsequently a Cartesian acquisition is performed when the second TI period has elapsed, and a radial acquisition is performed after the Cartesian acquisition, and the processing circuitry is further configured to generate a magnetic resonance image of an imaged region based on data obtained from the third pulse sequence and the fourth pulse sequence, wherein the processing circuitry is further configured to calculate, as an index, with respect to the imaged region, at least one of a peak signal value, a peak flow time, an arterial transit time, and a blood flow volume, based on the data obtained from the third pulse sequence and the fourth pulse sequence, the imaged region is a region in a brain, and the processing circuitry is further configured to predict a degree of a stenosis or an occlusion of a blood vessel based on a Magnetic Resonance Angiography (MRA) image and the calculated index.
 2. The magnetic resonance imaging apparatus according to claim 1, wherein the imaged region includes a region having one of microvascularization and microcirculation.
 3. The magnetic resonance imaging apparatus according to claim 1, wherein the processing circuitry is further configured to detect the stenosis, which is equal to or smaller than 50% of a diameter of a blood vessel, based on the index.
 4. The magnetic resonance imaging apparatus according to claim 1, wherein the processing circuitry is further configured to predict an abnormality in a perforator branch, based on the index.
 5. A magnetic resonance imaging method implemented by a magnetic resonance imaging apparatus, the magnetic resonance imaging method comprising: executing, by sequence controlling circuitry, (i) a first pulse sequence in which a spatially selective Inversion recovery (IR) pulse and a spatially non-selective IR pulse are applied, and subsequently a Cartesian acquisition is performed when a first Inversion Time (TI) period has elapsed, and a radial acquisition is performed after the Cartesian acquisition, and (ii) a second pulse sequence in which the spatially non-selective IR pulse is applied without applying the spatially selective IR pulse, and subsequently a Cartesian acquisition is performed when the first TI period has elapsed, and a radial acquisition is performed after the Cartesian acquisition, while varying the first TI period, with respect to a plurality of first TI periods; calculating, by processing circuitry, a second TI period to be used in a third pulse sequence and a fourth pulse sequence, based on data obtained from the first pulse sequence and the second pulse sequence; executing, by the sequence controlling circuitry, (iii) the third pulse sequence in which the spatially selective IR pulse and the spatially non-selective IR pulse are applied, and subsequently a Cartesian acquisition is performed when the second TI period has elapsed, and a radial acquisition is performed after the Cartesian acquisition, and (iv) the fourth pulse sequence in which the spatially non-selective IR pulse is applied without applying the spatially selective IR pulse, and subsequently a Cartesian acquisition is performed when the second TI period has elapsed, and a radial acquisition is performed after the Cartesian acquisition; and generating, by the processing circuitry, a magnetic resonance image of an imaged region based on data obtained from the third pulse sequence and the fourth pulse sequence, wherein the imaged region is a region in a brain, and the method further includes calculating, as an index, with respect to the imaged region, at least one of a peak signal value, a peak flow time, an arterial transit time, and a blood flow volume, based on the data obtained from the third pulse sequence and the fourth pulse sequence, and predicting a degree of a stenosis or an occlusion of a blood vessel based on a Magnetic Resonance Angiography (MRA) image and the calculated index. 